Covers for light poles, traffic signal poles, street sign poles, bollards, or utility poles have been used for many decades to add a decorative base to a light pole, or to hide and protect an access hole to wiring splices or fuses in the pole. Traditionally, these covers were made of cast iron and formed by statically pouring molten iron into sand molds. This process includes breaking out sand molds, finishing and painting the covers, and installing the covers onto the poles.
The cast iron covers are disadvantageous because they are heavy, expensive, brittle, corrosive in urban environments, and electrically conductive. More specifically, the cast iron covers present a shock hazard and are subject to galvanic corrosion. In addition, many of the foundries are no longer in business, and the original patterns for production have been lost. Other alternative covers are made of cast aluminum and cast concrete, both of which have several of the same drawbacks of the original cast iron covers.
In recent years, covers duplicating the old cast iron covers have been manufactured from fiberglass and polyester resin using traditional techniques such as hand lay-up or spray-chopped. These covers are light, non-corrosive, aesthetically pleasing, and inexpensive. In addition, they are less likely to cause damage or injury when hit by vehicles compared to the traditional covers.
Even more recently, covers have been manufactured by pouring a urethane into a mold, allowing it to cure, and removing the part. These covers possess the advantages associated with the fiberglass covers, and the urethane covers are more impact resistant and less expensive to produce.
To form a poured urethane (or resin injection molded) cover, a core is placed into a mold, and the urethane is poured or injected into the cavity formed by the outer mold and the core. After the urethane is polymerized, the core is extracted and the mold opened to remove the cover.
The disadvantage of the poured urethane method is that many of the more decorative covers have large undercuts, which prevent a core from being removed after molding. As a result, the wall thickness is much thicker than necessary in the undercut areas. These large variations in wall thickness increases the production cost and reduces the structural integrity of the cover. Since the cost of urethane is higher than the material cost of fiberglass, the cost advantages of lower labor costs for urethane covers is largely offset by the higher material costs. It would be commercially important if a urethane cover could be molded with a relatively constant wall thickness, thus minimizing both the material and labor costs. The described invention produces a uniform and stable wall section, with low labor cost.